1. Field of the Invention
This invention relates to a lubrication system for a one-way clutch.
2. Description of the Related Art
Among one-way clutches which can transmit rotating force in only one direction but idle in the opposite direction, so-called sprag or roller one-way clutches are widely used these days. In such a sprag or roller one-way clutch, clutch members such as sprags or rollers are arranged between an inner ring and an outer ring and are guided at both side walls thereof by end bearings, respectively, so that the clutch members engage the outer and inner rings upon transmission of rotating force but undergo sliding upon idling.
The fundamental construction of a one-way clutch is illustrated in FIG. 7, in which there are shown the one-way clutch 10, clutch members 11, left and right end bearings 12L, 12R, an inner ring 1, an outer ring 2, oilways 3,3' for introducing a lube oil into the one-way clutch, a presser plate (spacer) 4 for limiting the position of the one-way clutch in an axial direction, a stop ring 5, and a central axis X--X.
In a one-way clutch, clutch members repeatedly undergo engagement with an inner and outer rings and sliding due to idling. Substantial heat generation and friction therefore occur unless sufficient lubrication is applied. Further, it is also necessary to supply a lube oil sufficiently to avoid irregular rotation and/or seizure because end bearings are usually sliding bearings.
For this purpose, the one-way clutch is provided at mounting portions therefor with special lube oil passages like the oilways 3,3' in the inner and outer rings as shown in FIG. 7.
However, the arrangement of oilways as lube oil passages inside a power transmission mechanism of a complex construction as described above requires by itself complex machining and members provided with the oilways, such as an inner ring and an outer ring, are reduced in strength. Further, clutch members trample under a high bearing pressure the oilways open in raceway surfaces upon coupling of the one-way clutch. The oilways may therefore become as origins for the propagation of flaking and/or cracking, resulting in the problem that the raceway surfaces may be deteriorated.
To cope with this problem, it is often required to increase the thicknesses of the inner and outer rings and/or to use an expensive material for the inner and outer rings. These requirements however lead to improper deformation in heat treatment or the like, thereby necessitating complex treatment and machining.
It was hence proposed to arrange helical lube oil grooves open in relatively-rotating opposing walls of an inner or outer ring and an end bearing or presser plate instead of formation of oilways in peripheral members such as an inner and outer rings and then to make the helical lube oil grooves produce pumping action under the relative rotation to introduce a lube oil into a one-way clutch.
In each of FIGS. 6A and 6B, end bearings are indicated by numeral 12 (the left and right end bearings are designated at symbols 12L,12R, respectively), a central space with clutch members accommodated therein by letter C, a left-hand outer space by letter L, a right-hand outer space by letter R, an inner peripheral wall of each end bearing by numeral 121, and an outer peripheral wall of each end bearing by numeral 122. Each inner peripheral wall 121 is provided with helical oil grooves 123.
In FIG. 6A, the left and right end bearings 12L, 12R are provided with helical oil grooves 123A,123B both extending in a single common direction. In FIG. 6B, however, the helical oil grooves 123A in the left end bearing 12L and the helical oil grooves 123B in the right end bearing 12R are different in helically-winding direction from each other.
Since the left and right end bearings 12L,12R in FIG. 6A are of the same shape, end bearings of the same design can be used commonly as these bearings 12L,12R.
When the one-way clutch rotates in one direction in FIG. 6A, the oil flows from L to C as indicated by arrow D.sub.1 in the case of the end bearing 12L. Since the direction of each helical groove is the same in the end bearing 12R, the oil flows in the same direction as the arrow D.sub.1, that is, from C to R as indicated by arrow D.sub.3 in the case of the end bearing 12R.
In the case of a specification in which the direction of rotation is opposite, on the other hand, the direction of a flow of the oil becomes opposite as indicated by arrow D.sub.2 in the case of the end bearing 12L or by broken-line arrow D.sub.4 in the case of the end bearing 12R.
As is understood from the foregoing, inward flowing of the oil from L into C as indicated by arrow D.sub.1 is therefore accompanied by concurrent outward flowing of the oil from C to R as indicated by arrow D.sub.3. When the one-way clutch is rotating in the opposite direction, the oil flows in from R into C but at the same time, flows out from C to L as indicated by broken-line arrow D.sub.2. The space C in which the clutch members are accommodated cannot accordingly be filled with the lube oil.
FIG. 6B is a schematic illustration of flows of an oil when the left end bearing 12L and the right end bearing 12R are provided with helical oil grooves which are indicated at 123A,123B, respectively, and are different in helically-winding direction. When the one-way clutch is rotating in one direction, the oil flows from L into C as indicate by arrow D.sub.1 in the case of the end bearing 12L, and in the case of the end bearing 12R, the helical oil grooves 123B are opposite in helically-winding direction so that the oil flows from R into C as indicated by arrow D.sub.5.
In the case of a specification in which the direction of rotation of the one-way clutch is opposite, on the other hand, the direction of flows of the oil becomes opposite as indicated by broken-line arrows D.sub.2 and D.sub.6, respectively, so that the oil flows out from C to L in the case of the end bearing 12L and also from C to R in the case of the end bearing 12R.
As is appreciated from the foregoing, in the one-way clutch illustrated in FIG. 6B, the lube oil, depending on the direction of rotation, only flows into C from L and R or only flows out from C to L and R through both the end bearings 12L,12R. An oilway is therefore needed for discharging or feeding the lube oil, resulting in the drawback that the strength of the shaft is reduced.